Cellular Respiration Other Metabolites & Control of Respiration
Cellular respiration:
Beyond glucose: Other carbohydrates: Glycolysis accepts a wide range of carbohydrates fuels. polysaccharides glucose hydrolysis ex. starch, glycogen other 6C sugars glucose modified ex. galactose, fructose
Beyond glucose: Proteins proteins amino acids hydrolysis waste H H amino group = waste product excreted as ammonia, urea, or uric acid N H C R O C OH glycolysis Krebs cycle 2C sugar = carbon skeleton = enters glycolysis or Krebs cycle at different stages
Beyond glucose: Fats fats glycerol + fatty acids hydrolysis glycerol (3C) G3P glycolysis fatty acids 2C acetyl acetyl Krebs groups coa cycle 3C glycerol 2C fatty acids enters glycolysis as G3P enter Krebs cycle as acetyl CoA
Carbohydrates vs. Fats: Fat generates 2x ATP vs. carbohydrate more C in gram of fat more energy releasing bonds more O in gram of carbohydrate so it s already partly oxidized less energy to release carbohydrate That s why it takes so much to lose a pound a fat! fat
Metabolism: Coordination of chemical processes across whole organism digestion catabolism when organism needs energy or needs raw materials synthesis anabolism when organism has enough energy & a supply of raw materials by regulating enzymes feedback mechanisms raw materials stimulate production products inhibit further production CO 2
Metabolism: Digestion digestion of carbohydrates, fats & proteins all catabolized through same pathways enter at different points cell extracts energy from every source Cells are versatile & selfish! CO 2
Metabolism: Synthesis enough energy? build stuff! cell uses points in glycolysis & Krebs cycle as links to pathways for synthesis run pathways backwards have extra fuel, build fat! pyruvate glucose Krebs cycle intermediaries amino acids Cells are versatile & thrifty! acetyl CoA fatty acids
Carbohydrate Metabolism: The many stops on the Carbohydrate Line from Krebs cycle back through glycolysis gluconeogenesis
Lipid Metabolism: The many stops on the Lipid Line from Krebs cycle (acetyl CoA) to a variety of lipid synthesis pathways
Amino Acid Metabolism: The many stops on the Amino Acid Line from Krebs cycle & glycolysis to an array of amino acid synthesis pathways 8 essential amino acids 12 synthesized aa s
Nucleotide Metabolism: The many stops on the GATC Line sugar from glycolysis phosphate & N-base from Krebs cycle
Central Role of Acetyl CoA: Acetyl CoA is central to both energy production & biomolecule synthesis Depending on organism s need build ATP immediate use build fat stored energy CO 2 NAD + NADH Protein coenzyme A Pyruvate Fat Glycolysis Acetyl coa ATP Lipid Glucose Glycolysis Pyruvate oxidation Krebs cycle ETC acetyl group
Control of Respiration (Feedback Control) 2006-2007
Feedback Inhibition: Regulation & coordination of production final product is inhibitor of earlier step allosteric inhibitor of earlier enzyme no unnecessary accumulation of product production is self-limiting A B C D E F G X enzyme 1 enzyme 2 enzyme 3 enzyme 4 enzyme 5 enzyme 6 allosteric inhibitor of enzyme 1
Respond to cell s needs: Key point of control phosphofructokinase allosteric regulation of enzyme why here? can t turn back step before splitting glucose AMP & ADP stimulate ATP inhibits citrate inhibits Why is this regulation important? Balancing act: availability of raw materials vs. energy demands vs. synthesis
A Metabolic economy: Basic principles of supply & demand regulate metabolic economy balance the supply of raw materials with the products produced these molecules become feedback regulators they control enzymes at strategic points in glycolysis & Krebs cycle levels of AMP, ADP, ATP regulation by final products & raw materials levels of intermediates compounds in pathways regulation of earlier steps in pathways levels of other biomolecules in body regulates rate of siphoning off to synthesis pathways
It s a Balancing Act: Balancing synthesis with availability of both energy & raw materials is essential for survival! do it well & you survive longer you survive longer & you have more offspring you have more offspring & you get to take over the world Protein Glycolysis Pyruvate Lipid Glucose Glycolysis Pyruvate oxidation Krebs cycle ETC Fat ATP
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